1. Field of the Invention
This invention relates to a platform for mechanically guiding a circular power saw along a predetermined line to be cut. This platform can be adjusted to accommodate almost any size power circular saw that has a flat baseplate, and it has particular utility to unskilled craftsmen wishing to employ a circular power saw for woodworking projects, as well as to professional carpenters in need of cutting and trimming doors and other workpieces made of particle board, veneer, plywood, etc.
2. Description of the Prior Art
Portable circular power saws are widely used by carpenters on the construction site. Because such saws are relatively compact and inexpensive, they are also now widely used by homeowners.
In using such saws, there is a need for a saw guide which allows cuts to be done from near or to zero, or cuts less than the bite of the blade, as precisely and quickly as full cuts. When a power saw is free hand guided, it is nearly impossible to cleanly cut a workpiece from or to zero, or for a depth which is less than the bite of the blade. Generally, such cuts require planing or sanding to obtain a properly finished cut, but through the use of the platform saw guide of this invention, smooth cuts may be directly obtained. There is a further need for the saw guide to be useable with saws having differently-sized baseplates.
Various attempts have been already made to provide an adjustable guide which is adapted to orient the blades of power saws having flat baseplates of various sizes. All of such saw guides include a base member made of a material which is cut by the saw's own blade on the first cut thereof to custom fit the saw guide to the saw's particular base plate.
But, in using the known saw guides, one finds major drawbacks: (1) inability to make accurate long cuts, (2) a tendency for the workpiece to chip and splinter along the line of cut, when working with plywood, veneer, and particle boards such as masonite, (3) the guides are relatively slow and cumbersome to use, (4) the guides require separate clamping means, (5) most of them are too wide for say cabinet work, (6) they are relatively fragile and are subject to warping.
Various saw guide devices have been already patented whose primary object is to allow for the making of accurate long cuts. Such devices are described, for example, in U.S. Pat. Nos. 3,186,452, 3,741,063, 3,830,130, 3,874,261, 3,983,776, 4,028,976, 4,050,340, 4,059,038, 4,077,292 and 4,095,632.
One saw guide proposed for reducing splintering is described in U.S. Pat. No. 4,075,920, Neal. The Neal patent discloses a guide plate having a guide surface for guiding the baseplate's edge farthest from the saw blade, and an edge made in a trimable material for guiding the saw blade itself. This edge is cut to size by the blade upon its first cut. In contrast to the present invention, further adjusting cuts of this edge are difficult or impossible because the severable material portion may not be wide enough and is secured to the rest of the guide by a tongue-and-groove joint.
In the Neal device when a power saw having a larger baseplate is to be employed or when the blade-guiding edge becomes used up, a new piece of trimable material has to be added and the old one replaced thereby.
Renewable blade-guiding edges are required not only for differently-sized baseplates but also when the teeth of the saw blade wear down. Blunting of the blade's teeth is common due to hidden nails frequently found under veneer of doors, and also due to unavoidable wear.
An attempt to overcome the drawbacks encountered in the use of Neal's saw guide is described in U.S. Pat. No. 4,307,513, Genge.
The Genge saw guide includes a trimable base member made of an easily cutable material, such as masonite, and a shield member made of aluminum or steel which has the same width as the base member. The shield member is placed on top of and overlies the base member and is adjustably secured thereto by bolts. A clamp track and clamps are provided near the outer edge of the shield.
In use, the Genge saw guide is placed over and is clamped down to the workpiece with the base member being positioned to overhang the workpiece to facilitate cutting of the base member. The first cut produces an original blade guide edge which is obtained by severing a portion of the base member in order to custom fit the base member to the saw's baseplate which is positioned on top of the upper surface of that portion of the base member which is not being overlain by the shield member.
The edge of the saw's baseplate farthest from the saw blade abuts against the shield's inner edge which serves as a guide surface for the baseplate. The base member can be moved forward and recut to provide an adjusted guide edge. The distance from the guide surface to the adjusted guide edge will again accommodate the saw's baseplate, so that the saw blade will again abut and be guided by the adjusted guide edge of the base member. The entire weight of the saw rests on and is distributed over the portion of Genge's base member which is not overlain by the shield member. Splintering can occur because the lower surface of the base member is not tightly pressed against, and therefore does not provide adequate downward support for, that portion of the workpiece that is retained after the cut is made.
There is a tendency for Genge's base member to separate from his shield member which may cause the guide surface on the shield member to lose contact with the edge of the saw's baseplate resulting in a non-linear cut. Also, because the base member carries the entire weight of the saw, it tends to want to rotate relative to the overlaying shield member, further exacerbating the separation problem between the base and shield members.
It is a main object of the present invention to provide a new and improved platform for guiding circular power saws which overcomes the above-mentioned and other known drawbacks and problems associated with known saw guides, and to provide a relatively simple-to-construct platform which allows long, linear, splinterless cuts to be made with ease even by amateur carpenters. The benefits and advantages of the invention will become more apparent as the description proceeds.